class code4 {
    //&的进位相加  ^的不进位相加
    public int add(int a, int b) {
        int m = a ^ b;
        int n = (a & b) << 1;
        while(n != 0) {
            int tmp = n ^ m;
            n = (m & n) << 1;
            m = tmp;
        }
        return m;
    }
}